A young widow, Mizuki (Eri Fukatsu), gives piano lessons to children. One evening as she is preparing her dinner, the ghost of her husband, Yusuke (Tadanobu Asano) appears, three years after his drowing death. Rather than being shocked or surprised, Mizuki simply says, "Welcome home." He explains that his death was by suicide brought on by great depression, and that it had taken him three years to return to her. Yusuke asks Mizuki to go on a long journey with him, showing her places he had been.

The couple travels by train to a town, where he introduces her to Shimakage (Masao Komatsu), an old man with a newspaper distribution business who Yusuke had assisted during his journey. Shimakage bemoans the fact that he had treated his wife poorly, and that she had left him. Yusuke tells Mizuki that the old man is like him, but doesn't know he is dead. When the realization comes to him, he vanishes and his home's appearance becomes that of a long-abandoned ruin. Mizuki and Yusuke then travel to a Chinese diner, run by an industrious couple, Jinnai and Fuji. Finding a piano in restaurant's part room, Mizuki starts to play a favorite tune, "Harmony of the Angels". But Fujie interrupts, sorrowfully explaining that that the song had been played, poorly, over and over by their young daughter who had died. Fujie was distraught because she had chastised the daughter for continuing to try to play it. The ghost of the little girl appears and plays the song masterfully, to Fujie's joy.

They then go to a farming community, where the villagers are very happy to see Yusuke again, and they excitedly gather in a large tent. They listen with rapt attention as Yusuke lectures to them about quantum physics.

Mizuki experiences other encounters: The ghost of her father appears to her and urges her to leave Yusuke. She follows a young boy into the forest where he points to a cave below a waterfall and tells her that is the way to the other world. She watches as Yusuke convinces another reluctant ghost to accept his situation.

Finally, Yusuke makes his final departure from the world, but not before he and Muzuki make love.